1. Field of the Invention
The present invention relates to motor vehicles, and more particularly to a cooling arrangement for an electrical machine of a vehicle, the electrical machine being connected to the engine block of the vehicle.
2. Description of the Related Art
Such electrical machines are, for example, synchronous machines for generating electrical energy. The generated electrical energy is then made available to all kinds of devices in the vehicle. Among other things, a heat loss, which as a rule results from copper losses and iron losses, is produced during the operation of such electrical machines. However, the heat loss in the electrical machine is undesirable, since it may lead to power losses of the machine and to damage of the latter in the worst case.
The electrical machine must therefore be cooled in order to reduce the heat loss produced in it. To this end, cooling arrangements independent of the electrical machine have been used heretofore. Such cooling arrangements contain, for example, heat exchangers or the like, which are connected to the coolant circuit via appropriate devices such as pumps, etc.
However, the known solutions have a number of disadvantages. First of all, the electrical machine itself has co be provided with appropriate cooling elements. Thus cooling of the electrical machine is only possible at a high design cost. Furthermore, a number of secondary units are required in order to provide a suitable circulation of the coolant. The known cooling arrangements are therefore also relatively costly.
In vehicles with a limited amount of space available in the engine compartment, the known cooling arrangements are particularly disadvantageous in that an excessive amount of the installation space, which is limited anyway, is taken up by a multiplicity of requisite secondary units. Finally, some of the secondary units, such as pumps for example, in turn consume electrical energy, a factor which has an adverse effect on the energy balance of the electrical machine.
Starting from the aforesaid prior art, it is an object of the present invention to provide a cooling arrangement with which the disadvantages described can be avoided. In particular, a cooling arrangement with which cooling of the electrical machine can be realized in a simple and cost-effective manner is to be provided.
This and other objects are achieved by a cooling arrangement which, according to the invention, comprises a support element on the electrical machine, and a cooling element on the engine block. At least a region of the electrical machine is connected to the cooling element of the engine block via the support element such that heat generated during operation of the electrical machine is dissipated or can be dissipated thermally into the engine block.
Such a cooling arrangement can be realized in a simple and cost-effective manner. The basic idea of the present invention lies in the fact that the electrical machine is thermally connected to the engine block. This thermal connection is effected via the support element and the cooling element. In this case, the heat loss produced in the electrical machine is dissipated into the engine block via the support element, which is preferably an integral part of the electrical machine. The secondary units, such as heat exchangers, pumps or the like, previously required for the cooling of the electrical machine may also be dispensed with. Furthermore, the prior requisite separate cooling of the casing of tile electrical machine is also dispensed with.
The engine for the vehicle may be a conventional internal combustion engine, which, depending on tile embodiment, has a one-piece or multi-piece engine block. The present invention is not restricted to special engine types, since cooling is effected only via the support element of the electrical machine and the cooling element of the engine block, and these two components, depending on the application, may be of any desired design. The only precondition is that good heat transfer between the two elements is ensured.
The electrical machines used may be, for example, synchronous machines and here, in particular, permanent-field synchronous machines. A machine especially worth mentioning is, for example, the starter-generator for vehicles. This is an electrical machine whose rotors are mounted via a crankshaft bearing arrangement of the internal combustion engine. The starter-generator is not only used for starting and stopping the engine but may also perform various functions during the engine operation, such as, for example, braking functions, booster functions, battery management, active vibration damping, synchronization of the internal combustion engine or the like.
Such a starter-generator is designed, for example, as an external-rotor synchronous machine and is connected to the engine block of the internal combustion engine via a stator support as support element. Such machines are especially suited for the heat-conduction cooling according to the invention, since the heat loss inside the machine can be dissipated therefrom directly into the engine block in a simple manner via the stator support and the cooling element of the engine block.
At least a region of the end face of the support element can advantageously bear flat against the end face of the cooling element and essentially free of gaps. Good heat transfer is thereby provided between the cooling element and the support element, resulting in a further improvement of the dissipation of the heat loss produced in the electrical machine into the engine block. To enlarge the surface provided for the thermal transfer, the end face of the support element and/or of the cooling element may of course also be designed such that it is not flat.
In a further embodiment, the cooling element may be provided on an end face of the engine block. In this case, the cooling element is advantageously designed such that good heat transfer is ensured. In principle, both end faces of the engine block are possible for the arrangement of the cooling element. However, the cooling element is preferably arranged on that end face of the engine block which faces the transmission. Furthermore, it is also possible for the electrical machine to be fastened to the cooling element via the support element.
The cooling element may also be designed, for example, as an integral section of the engine block. As a result, the cooling element may be produced directly along with the engine block in one operation during the manufacture of the engine blockxe2x80x94for instance by a casting process, a factor which constitutes a solution which is simple in terms of design and is cost-effective.
However, it is also conceivable for the cooling element to first of all be produced as a separate component and to then be connected to the engine block. With such a solution, a, material having especially pronounced heat-conduction properties could be used, for example, for the cooling element. This would result in the heat transfer between the electrical machine and the engine block being further improved. Such a separately produced cooling element may be suitably connected to the engine block in a detachable manner or by cohesive bonding. Examples of advantageous types of connection are, inter alia, welded connections, screwed connections or the like. In particular in the case of a screwed connection, the cooling element may be additionally positioned via mating pins, mating sleeves or a centering diameter.
Since the end face of the engine block generally has a number of webs, projections, bulges and the like, which extend outward from the end face of the engine block, the cooling element is preferably of a height which approximately corresponds to the height of the elements described above. The cooling element may of course be of a different height.
In a further embodiment, the cooling element may be design as a ring element. The cooling element designed in such a way is preferably arranged concentrically around the crankshaft of the engine block. The ring element may be designed, for example, as a continuous ring, as a result of which the area for the heat transfer is increased further. Such a design of the cooling element is appropriate, for example, when the engine block is of one-piece design. Given appropriate dimensioning of the cooling element, the support element of the electrical machine may also be fastened to the cooling element at the same time.
In another embodiment, the cooling element may be formed from a number of cooling-element segments. In this case, the cooling-element segments may be ring segments which have an intermediate space between them Such a design is appropriate, for example, when the engine block is of multi-piece design and each cooling-element segment is produced together with the respective part of the engine block.
The invention is of course not restricted to special geometries and sizes of the cooling-element segments. On the contrary, the size and/or shape of the cooling-element segments, depending on requirement and application, may be selected as desired. As a result, effective heat-conduction cooling can be realized even in the case of complicated types of engine construction. The only precondition is that the cooling element in its entirety has a sufficiently large area in order to dissipate the heat transferred via the support element of the electrical machine.
The electrical machine can preferably be detachably connected to the cooling element of the engine block via the support element. Such a connection may be produced, for example, via a suitable screwed connection. in this case, the support element may be connected to the cooling element of the engine block or else directly to the engine block itself. In addition, mating pins, mating sleeves or a centering diameter may be provided for the positioning of the support element.
In yet a further embodiment, at least one cooling helix or a least one cooling passage is provided in the cooling element. As a result, the dissipation of the heat loss from the electrical machine and thus its cooling may be further improved. The cooling helix or the cooling passage may advantageously be designed as an open groove construction on that end face of the cooling element which faces the support element. The production of such a cooling helix or such a cooling passage is especially simple and cost-effective.
In another embodiment, at least one cooling helix or at least one cooling passage is provided in the support element, As a result, additional cooling of the electrical machine is achieved.
The cooling helix or the cooling passage is preferably designed as an open groove construction on that end face of the support element which faces the cooling element.
In a design of the cooling helix or of the cooling passage as an open groove construction on either the cooling element or the support element, the other respective element which does not have such a groove construction, can seal off the corresponding groove, as a result of which a closed cooling helix overall or a cooling passage is obtained. The production of such a groove construction is especially simple. Furthermore, the coolant flowing through the cooling passage or the cooling helix, from the cooling system of the engine block can act at the direct transition between the support element and the cooling element (the location of the direct heat transfer), as a result of which the cooling effect is fixer improved.
The open groove constructions of the cooling element and the support element may advantageously be arranged one on top of the other. When an open groove construction is used in both the cooling element and the support element, the cross section of the entire cooling helix or of the entire cooling passage can be enlarged, which is advantageous for the cooling effect.
In a further refinement, the cooling helix or the cooling passage of the support element and/or of the cooling element may be connected to a cooling system of the engine block. As a result, use may be made of already existing cooling systems of the engine block in a simple manner for the additional cooling.
Advantageously at least a region of the cooling element and/or of the support element may be formed from a material having a high thermal conductivity. As a result, the heat conduction is increased further. For example, it is conceivable for the cooling element and/or the support element to be of sandwich-like construction, individual layers being formed from the especially heat-conductive material. Other embodiments in which the elements are formed from such an especially good heat-conducting material only in quite specific defined regions are of course also conceivable. As a result, regions with preferred heat conduction can be deliberately produced. In an advantageous embodiment, the entire cooling element and/or support element may be formed from a material having especially good heat conductivity.
In a further embodiment, a coolant having high thermal conductivity may be provided in or may be capable of being directed into the cooling helix or the cooling passage of the support element and/or of the cooling element. As a result, the heat transfer between the two elements is further improved. In principle, solid, liquid and gaseous substances are conceivable as the coolant.
The invention is not restricted to special materials or coolants with high thermal conductivity, however, among other things, a sodium based or Fregen substitutes are conceivable.
In yet a further embodiment, the at least one cooling helix or the at least one cooling passage of the cooling element and of the support element may be connected to one another via a connecting element. If the cooling helix or the cooling passage is formed only in the support element or the cooling element, this cooling helix/cooling passage may be connected to the cooling system of the engine block via a corresponding connecting element. By the use of such a connecting element, which is preferably made of an elastic material, the connection between the cooling helices or cooling passages to each other or to the cooling system can be rendered flexible, as a result of which, production tolerances can be compensated for.
The connecting element preferably has at least one sealing element. Such a sealing element which may be, for example, an O-ring or the like.
The above-described cooling arrangement according to the invention may be advantageously used for cooling a permanent-field synchronous machine, preferably a starter-generator, arranged on an engine block of a vehicle.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of the disclosure. For a better understanding of the invention, its operating advantages, and specific object attained by its use, reference should be had to the drawing and descriptive matter in which there are illustrated and described preferred embodiments of the invention.